Aperture priority (A) exposure mode is not applicable with a MF lens, since aperture cannot be set with the dials on the A7. M and S modes are very usable, on the other hand, along with manual or automatic ISO.

great summary Miki!

just...A mode works very well, also with manual ISO or auto ISO, only difference is that aperture is set on the lens, not on the camera

So, you have to set the aperture on the lens, and then also set the same aperture on the camera?